Telephone system



July 3, 1928. 1,615,956

L. F. PORTER TELEPHONE SYSTEM Filed May 25, 1927 5 Sheets-Sheet l /NVENTo/ l mL/f f PUHTER 5y v l I v s A ,47m/MEV July 3, 192s. 1,575,956

L. F. PORTER TELEPHONE SYSTEM Filed May 25, 1927 5 sheetysheet 2 /NVEN Tof? ESL/E P05727? Patented July 3, 1928.

vUNIfrlezo s'rA'res LESLIE F. PORTER, OF PASSAIC, NEI/V {l'EIS EY, ASSIGNOR TO BELL TELEPHONE LAB- ORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application liled May 25,

This invention relates to telephone systems and particularly to toll switching systems wherein cord circuits each comprising under normal conditions a clear pair of conductors are employed to establish connections over toll switching trunks each including` a train of automatic switches.

In accordance with one feature of the invention discriminating` means is provided in a common dialing circuit responsive to conditions found in different character trunk lines for automatically adapting the said common dialing circuit to the particular trunk line in use. Heretofore, as shown for example in Patent No. 1,567,256. to Fowler, a dialing` circuit has been provided which may be automatically adapted to ditferent character trunk lines. The present invention, however, deals with a different character cord circuit in which it is necessary to maintain a clear pair of conductors for a talking circuit. Since supervisory means can not he placed in association with the talking circuit, it is necessary7 to use the sleeve circuit for performing' the supervisory functions. Therefore, discriminating means has heen placed in "the dialing circuit itself. The present invention, therefore, dilferentiates from systems such as that shown in the patent to Fowler in two respects: one, the discriminating viii-.2ans 'for automatically adapting the dialing circuit to different trunk line `conditions is placed in the dialing circuititself; and, second, this discriminating means has been made common to the cord circuit.

In accordance with another feature of this invention a means is provided for automaticallyl applying ringing` current to a. trunk line for a single period of time of predetermined duration. Sehen of this Vature comprising a time counting arrangement individual to the trunks have been used heretofore, so that the present feature is in the nature of ai improvement, over such prior art arrangements. The new arrangement herein disclosed comprises a means common to the trunk line, that is, a means located in the cord circuit. More specifically, the time counting' arrangeuiicnt is common to the cord circuits that are, in turn, common to the trunks, so that a great i i (TS 1927. Serial No. 194,014.

economy and a corresponding simplicity in the circuits have been achieved.

In accordance with another feature of this invention means for applying ringing current to the trunk line is made to operate automatically and in response to the setting' of a switch over the trunk line. Vhen the connector has been set on the terminals of the called line, current in the trunlf` line is reversed and a polarized relay in the dialing circuit common to the cord circuits isoperated and this, in turn, causes the energization of a ringing' start relay which is limited in the duration of the time of its operation by a set of time counting; relays set in operation by the polarized relay.

ln accordance with still another feature there is proifided a means for listening; and talking on a second cord circuit by opeiatingr a listening' ltey on such second cord circuit. Inder ordinary conditions the operation of a listening hey cuts off the operators transmitter and leaves only the operators receiver in connection with the cord circuit. Also under ordinary conditions the operation of a talking` key exclusively associates considerable common apparatus `with the cord circuit so that if while the operator is using a certain cord circuit a connection on another cord circuit requires attention, it would he impossible to give such attention without entirely abandoning' the oi'ierations of the Viirst cord circuit. A monitoring cut-oil relay is therefore provided so that hy operating' the listening' key of a second cord circuit the operator may tall; over a second cord circuit without either cutting' ofil the transmitter or disturhinfg,r the common apparatus now connected to the first cord circuit.

In 'the drawings a telephone system err hodyingy among others the ahove described features is shown in diagrammatic form. In Fig. l there is shown a cord circuit and certain of the circuits and apparatus common thereto. In Fic'. 2 there is shown the remainder of the circuits and apparatus common to the cord circuit of Fig. l. In Fig. 3 there is shown a repeated dialing trunk and in Fig. i there is shown a loop dialing` trunk hoth. adapted to cooperate with the cord circuit of Fig. l.

TWhen the operator Wishes to establish a connection over the repeated dialing trunk shown in llig. 3 She inserts plug 1041 in acl-t 301. She then operates the talking lrey T individual to the cord circuit and the front dialing' ley 203 common to the cord circuit whereupon. a circuit is established from ground, lett hand high resistance Winding ot sleeve relay 302, sleeve of jack 301, sleeve or' plug 104 through the (3th and 7th springs ot' lrey T (tounting trom the bottom), conductor 107, lower contacts olf the iront dial release liey 201, conductor S, Winding;` oil nnirpinal relay 109, Windingot relay 110 to battery and l'iound. Relay 110 and relay 302 become actuated in this circuit, but relay `109 does not operate due to the sistance ot' this circuit. lt will later be shown bow this resistance lowered by a parallel circuit throufrhthe right hand low resistance Winding` or relay 302 whereupon relay 109 will operate. Through the actuation ol' key T a circuit is established from battery, right hand Windingv o1 relay 103? the 13th and 14th contact spring/js or lrey T, conductor 112, and the normal Contact ot relay 111 to ground. Relay 103 beconies energized in this circuit and establishes a connection through its outer right hand armature and liront contact and conductor 11S for the encre-ization of relay 111. Relay 111 now transrers the ground connection from -onductor 112 to conductor 113 Whereupon ground is extended through 'the 11th and 12th springs of key T to the inner left hand armature and front Contact or relay 103, thence through the lett hand WindingI ot relay 103 to battery to hold this relay locked so that as long as the lrey T is in its operated position relay 103 individual to the cord circuit and relay 111, common to the cord circuit are op rated. Relay 103 splits the cord and associates the group ot conductors 11/1 with the cord circuit.

Upon the operation of relay 110 a circuit is established from ground, armature and front contact oi relay 110, Winding4 ot relay 202 to battery and ground. Relay 202 becomes operated and extends the `ground on conductor 113 through the back contact and outer right hand armature ot relay 205, the lower contacts ot iront dialing;` key 203, the lowerinost armature and front contact of relay 202, conductor 115 to the Windingr ot relay 116, common to the cord circuits. 116 operates in this circuit. rllhe ,ground on conductor 113 is also extended through the outer lett hand armature and back Contact of relay 121, the normal contacts oit relay G, armature and back corr tact ot polarized relay 120, front Contact and outer right hand armature ot relay 110, conductor 122. upper contacts of 'front dial release lrey 201, normal contacts ot the lett hand armature of relay 207, Windingw oi relay 125 to ground. Relay 125 becomes operated i this circuit and by attractingY its armature establislies an obvious circuit Yl'or relay 20T. Relay 207 now loclfs in to the ground pro-4 vided 'lor the energization oit relay 125 ano relay 125 remains operated in a circuit. eX-

' ne; from battery, Winding ot relay 125, u ridingl ot marginal relay 120, trout contant and right hand arn'iature olf relay 125, baclr contact and lett hand armature ol relay 20S, normal contacts or the inner lett hand armature of relay 121, inner lei't hand armature and alternate contact ol relay 110, iront Contact, and outer le't hand armature of relay 108, normal lon'er contacts ot liront rinsing; lrey 119, tip ot plug 10i, tip oit jack 301` upper armature and back contact o1 rclay 303, Windingof relay 301 to ground. llelay 301 being` o1l low resistance causes the operation of relay 126 as Well as the operation ot relays 125 and 304:. Thereupon a circuit is closed from ground, armature and Jfrontcontact of relay 120, norinal contacts oit the outer right hand armature oli relay 121, Winding' of relay 209 to battery and ground. Relay 209, known as the repeated dialing relay now establishes` a circuit. 'roni battery through resistance 123, front contact and lett hand armature ot relay 209` contacts of dial 129, Winding ot polarized relay 120. inner rurht hand armature and alternate contact o1 relay 116, trout contact and inner right hand armature ot relay 103, ringot plug 10a, ring of jacl; 301, lower armature and baclr contact o1 relay 303, WindingY or relay 305, to ground, resulting in the energization of relay 305.

Upon the operation or relay 209 a circuit is established troni `ground, the upper contacts of front dialinov key 203, right hand arma-ture, and iront contact ot relay 209, Winding of relay 121 to battery. Relay 121 becoming energized establishes a substitute circuit for relay 209 extendingl from ground, outer right hand armature and 'liront contact of relay 121, through the Windingof relay 209 to battery and t(ground. Relay 121 also provides a lockingY circuit 'for relay 11b over its inner right hand armature an d trout coutact. Relay 121 now substitutes battery through resistance 130 in place o1 battery through the windings ot relays 125 and 120 and these latter relays become deenergized. Relay 121 also opens the circuit ot relay 20T and this relay releases. The circuit tluough the lett hand arinature und back Contact ot relay 125, right hand armature and front Contact of relay 207, windin;` ot relay 210 to battery and ground is not eiliectiyely tablished at this time since the deenergization of relays 125 and 207 is controlled by relay 121. Since relay 20T is controlled by a simple back contact of relay 121, relay 20T will open its right hand Contact before relay 125 can close its lett hand back contact.

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lVith relays 304 and 305 energized, a circuit is established from ground on conductor 306 through the armature and back contact ot relay 307, Winding of relay 303, inner right hand armature and back contact of relay 309, Winding ot polarized relay 310, ari'nature and front Contact ot relay 305, right hand armature and trontcontact of relay 304, conductor 311, resistance 312, back contact and lower armature of relay 307, to battery on conductor 313. Conductors 300 and 313 entend to an automatic s itch such for instance that shown in Fig. 3 or' Patent No. 1,474,003 to Stoliely and as there shown are connected through the windings of' the line relay to ground and battery respectively. Thus a bridge tor the energization ot the distant selector line relay is established. Relay 303 is energized in this bridge circuit.

The energization ot relay 304 opens the circuit of relay 303 so that it cannot operate at this time. The energization ot relay 304 also establishes a circuit from battery, left hand armature and back Contact ot relay 309, resistance 314, front contact and inner lett hand armature ol relay 304, baci; contact and right hand armature ot relay 315, Winding of relay 316 to ground. Relay 316 becomes energized and closes a circuit from ground, the right hand armature and vliront contact ot relay 302, the front contact and inner lett hand armature of relay 316 through the Winding ot relay 315 to battery and ground and relay 315 through its front contactand lett hand armature locks to the ground supplied by the right hand armature ot relay 302. The original energizing circuit or relay 316 is nonT opened but an alternate circuit is provided so that relay 316 remains energized in a circuit from battery, lett hand armature and back contact ot relay 309, resistance 314, front contact and right hand armature of relay 315, Winding ot relay 316 to ground.

The dialing circuit is now complete, relay 305 being energized in series with the dial 129 and resistance 123 to battery. The operator will actuate dial 129 to send out an appropriate number ot trains ot impulses which each in the torni oit a series or short interruptions ot the circuit through rela-y 305. Relay 305 responds to each impulse by opening its cont-act. This, in turn, opens the bridge across the trunk leading from the right hand portion ot Fig. 3 and thus operaltes the line relay in the distant selector circuit to set up a connection in the manner fully explained in the Stoliely Patent 1,474,- 003 hereinbe'fore referred to. Relay 308 in this bridge circuit responds to each impulse by closing its armature and contact and this in turn completes a short circuitabout the Winding ot relay 316, the circuit extending from the armature and back contact oi relay 308, the inner lett hand armature and front contact ot relay 304, the iront contact and right hand armature oit relay 315 to the Winding ot relay 316. The period ot each ot these short-circuits, however, is very small and relay 316 being slow to release does not respond by returning to normal but, on the other hand, remains in its operated position.

Ii', during the dialing period an all terminals busy condition is encountered the talking circuit is opened momentarily. This causes relay 303 to become deenergized for a period longer than the duration of an impulse and thereupon relay 316 becomes deenergized through having its winding short circuited. Upon the deenergization ot relay 316, a circuit is established i'rom ground, right hand armature and front Contact of relay 302, left hand armature and front contact of relay 315, inner lett hand armature and back contact of relay 316, Winding ot relay 309 to battery and ground. Relay 309 becomes energized and permanently opens the bridge across the outgoing end of the trunk. Relay 309 also closes a circuit from ground, interrupter 317, iront Contact and outer right hand armature ot' relay 309, baclr contact and right hand armature oi' relay 316, back Contact and outermost lower armature of relay 313, baclrv contact and right armature of relay 319, right hand 10W resistance Winding of relay 302, sleeve of jack 301, sleeve ot plug 104, 6th and 7 th contact springs of key T, conductor 107, lower contact springs of dial release key 201, Windings ot marginal relay 109 and relay 110 to battery and ground. Since the resistance of the original circuit through relays 109 and 110 is now lowered by this parallel circuit through the right hand Winding of relay 302, the ii'iarginal relay 109 Will become energized. T he energization of marginal relay 109 will be periodic, following the impulses set up through the interrupter 317. During the period when relay 109 is deenergized a circuit is established from battery, lamp 124, the 3rd and 4th contact springs ot key T, conductor 117, high resistance 127, front contact and inner upper armature of relay 202 to ground. Due to the resistance 127, lamp 124 does not become suiliciently illuminated to be visible. During the periods when relay 109 is operated, resistance 127 is shunted by low resistance 131 and this so increases the current flow in lamp 124 that it becomes illuminated, and thus lamp 124 flashes in maison With the interrupter 317. lt should be noted that the circuit through resistance 131 leads through the trent contact out relay 109 and thence through the back Contact and right hand armature of relay 209. Since this latter relay is energized as Aong as dialing key 203 is actuated the above described flashing circuit will `be ineliective. As soon, however, as key 203 is returned to normal relays 121 and 209 will return to normal and lamp 124 will begin to Hash. l

Should the talking key T be released at this time, the. circuit for flashing' lamp 124 would extend over the sleeve of plug 104 through the 5th and 7th cont-act springs of key T directly to the lamp 124 so that the alternate establishment oi a ground path in parallel with the left hand winding ot' relay 302 wouldaccomplish the same result with regard -to lamp A124 as the shunting olf resistance 127 by resistance 131.

Should the called line prove to be busy, relay 316 remains in its operated position, and interrupter 320, designed to transmit impulses-at a higher rate, will operate over the -circuit just described for interrupter 317 so that the lamp 124 will flash at a correspondingly higher rate. The circuit for interrupter 320 of course, is established as soon as the dialing circuit is completed but the lamp 124 is prevented :trom giving the busy indication as long as the dialing key is operated, as above described. The operator, however, would have no occasion to release fthe dialing key until she had completed the .dialing yoperation so there is no danger that the busy signal whichl could be made to operate before the called line were even seized ywould be mistaken.

. ln case the called line proves to be idle, then the circuit for interrupter 320 is opened immediately after the last series of impulses has been sent. This is accomplished by the reversal of the current How in the trunk by the connector in the well known manner and the consequent operation of polarized relay 310.

Upon the operation of polarized relay 310, an obvious circuit for relay 313 is closed, rwhereupon this relay becomes energized, locks up under control of relay 302, and connects the repeating coil 321 to the trunk conductors leading to the right of Fig. 3. Relay 319 is now bridged across the trunk and will become energized by the battery supplied from the connector. Upon its energization, relay 319 `closes a circuit from ground, front contact and right hand armature of relay 319, through the right hand low resistance winding of relay 302 to cause the operation of marginal relay 109 and `to in turn cause the illumination of lamp 124 as a signal that the called line has been seized. A circuit is also closed Afrom ground, right hand armature and front contact ot relay 302, armature 322 and front contact of relay 318, winding o1 relay 309, to battery and ground whereupon vrelay 309 attracts its armatures and opens the bridge including the windings ot relays 303 vand 310. `At its left hand armature, relay 309 also opensthe circuit of relay 316 so that this relay vnow becomes deenergized. Relay 315, however, is maintained energized under control ot relay 302.

The operator will now release dialing key 203 whereupon relays 11G, 121 and 209 are released. Upon the release oit' relay 11G the, energizing circuit tor relay 304 is open and relay 304 in restoring its armatures to normal establishes a `circuit iirom ground, right hand armature and iront contact ot relay 302, front Contact and the second lower armature ot' relay 313, the back contact and outer lett hand armature ot relay 304, winding of relay 303 to battery and ground. llelay 303 now becomes energized and connects the tip and ring` conductors trom jack 301 to the windings ot repeating coil 321. A talking circuit may now be traced trom the lower left hand winding' ot repeating coil 321, front contact and .lower armature ot' relay 303, ring conductor ot jack 301, ring conductor of plug` 104, inner right hand armature and iront contact ot' relay 103, normal contacts ot the inner right hand armature ot relay 116, lower contacts ot the liront splitting key 212, inner lower armature and iront contact ot' relay 202, conductor 213, winding of induction coil 215I` conductor 216. iti-ont contact and upper outer armature of relay 202, upper contacts ot .front splitting` key 212, normal contacts oit the outer lett hand arma ture ot relay 116, front contact and outer lel't hand armature ot relay 103, lower normal contacts ot front ringing key 119, tip of plug 104, tip of `iack 301, upper armature and l-'ront contact o1 relay 303, and upper lett hand winding of repeating coil 321. The operators telephone set designated in general by the numeral 217 is associated with the windings ol induction coil 215 and hence the operator may communicate over the trunk circuit while the circuits are in this condition. As soon as the operator is ready, she will actuate the trunk ringing key 119 whereupon a circuit is established from battery, resistance 213, conductor 132, front contact of the lower contactset of front ringin key 119, tip of plug 104, tip of jack 301, upper armature and front contact of relay 303, upper left hand winding oit repeating` coil 321, winding ot ringing relay 307, to ground. Relay 307 becomes actuated in this circuit and applies ringing current to the conductors of the trunk leading to the called partys telephone. lVhen the called party answers, current will be disconnected from the trunk in the manner explained in the patent to Stokely No. 1,474,003 and relay 319 will become deenergized. Upon the deenergization of this relay, the low resistance circuit through the right hand winding ol relay 302 will be opened and relay 109 will become deenergized thus causing signal lamp 124 to become darkened as a signal that the called party has answered. The operator may now converse with the called party` over the talkllo Sii

Il l) ing circuit above described and when the connection through the rear plug 133 is properly established, the operator Will restore her talking key T to normal leaving a clear path between the calling` and called parties. Such a clear path may be traced 'trom the ring ot plug 133, through the back contact and right hand armature of relay 103 to the ring ot plug 104- and from the tip of plug 133 through the normal upper contacts ot rear ringing key 1341-, the back contact ot the outer' lett hand arn'iatureot relav 103, normal lower contacts oit front rino: 10 liey 119 to the tip ot plug 1011. When the conversation has ceased and the called party replaces his receiver on its hook, current will again be applied to the repeated dialing trunk and relay 31.9 Will become energized, whereupon the circuit through the low r sistance right hand Winding oit' relay 302 Will be closed and the signal lamp 1241 will become illuminated asa disconnect signal.

Vvllien the operator Wishes to establish a connection over either of the trunks shown in Figs. 3 or 1, she i'irst touches the tip ot plug 1041 to the sleeve of either jack 301 or A101. Under the idle condition ground potential is placed on the sleeve oi the jaclr but when the trunk is busy battery potential will be found at this point and a circuit will be established from battery, tip ot plug 1041, the normal contacts o1' the lower set olf rront ringing liey 119, outer lett hand arn'iature and trent contact oi relay 103, normal contacts of the outer left hand armature ot relay 11(3,upper contacts of `front splitting key 212, upper outer armature and back contact ot relay 202, right hand winding of repeating coil 211 to ground. Repeating coil 211 induces in the secondary Winding an iinpulse of current which vfill travel troni the louer terminal of the lett hand Winding oit repeating coil 214;. back contact and inner upper armature ot relay 221 through the operators receiver, the inner lower armature and back contact of relay 221, the condenser 222 to the upper terminal ot the upper lett hand Winding ot repeating coil 211. This impulse Will cause a click in the receiver and will be taken by the operator as a busy ini tion.

hen the operator Wishes to establish a connection over the loop dialing trunk shown in Fig. 1 she inserts plug 101 into jack 101. She then operates the talking key T and the trontdialing ley as before. A circuit is nouv established from ground, lett hand high resistance winding of sleeve relay sleeve of ack 101, sleeve of plug 101 through the 6th and 7th contact springs (counting from the bottom) ot key T conductor 107, lovver contacts ot trent dial reease key 201, conductor 103, Winding ot marginal relay 100, ivindiirg` ot relay 110 to battery and ground. Relay 110 and relay 102 become actuated in this circuit but relay 100 does not operate due to the high resist- .Il J. ,I

ance or the lelt hand Winding ot relay 102. Relay 103 becomes energized in the manner hercinbe'tore described and causes in turn the energization of relay 111. Relay 111 in turn places ground on conductor 113.

Unon the operation of relay 110 a circuit is established from ground, armature and l'ront contact of relay 110, Winding ol relay 202 to battery and ground. Relay 202 bccoines operated and extends the ground on conductor 113 through the back contact and outer right hand armature ot relay 205 and loiver contacts of tront dialing lrey 203, the lovermost armature and liront contact of re aj 202, conductor 115 to the Winding of relay 116 Which thereupon becomes operated. The ground on the conductor 113 is also eX- 'tended through the outer lett hand armature and back contact ot relay 121, the normal contacts ot relay 206, armature and back contact ot polarized relay 120, front contact and outer right hand armature oit relay 116, conductor 122, upper contacts o'l' front dial release key 201, normal contacts ot the left hund armature oit relay 207, Winding ot' rclay 125 to ground. Relay 125 becomes opcrated in this circuit and by attracting its arniature establishes an obvious circuit for relay 207. Relay 207 new locks into the ground providing for the energization oit relay 125 and relay 125 remains operated in a circuit extending from battery, Winding ot relay 125, Winding of marginal relay 120, front contact and right hand armature ot relay 125, back contact and lett hand arma.- ture ot' relay 208, normal contacts ot the inner lett hand armature o'l relay 121, inner lett hand armature and contact et relay 110, liront contact of outer lett hand armature ot relay 103, normal lower contacts ot trent ringing key 119, tip of plug 101, tip ot jack 401, upper armature and bacl contacts ot relay 103, Winding ot relay 103 to ground. relay 103 operates in this circuit and locks in a circuit including battery, the right hand armature and trent contact of relay 102, the alternate contacts ot the upper armature ot relay 103, Winding of relay 403 to ground. Due to the relatively high resistance o1l relay 103, marginal relay 126 does not become op-- erated prior to the operation ot relay 103 and upon the operation of relay 103 the circuit ot relays 125 and 126 becoming open causes the deenergization of both these re lays. Since relay 126 tails to operate at this time, neit-her relays 209, nor 121 become operated. Upon the release ot relay 125 a connection is extended trom ground, the lett hand armature and back contact ot relay 125, right hand armature and trent contact ot relay 207, Winding ot relay 210 to battery andy ground. Relay 210 becoming operated 'closes a circuit through the normal contacts of relay 219 to the winding ot relay 211, which now beconies operated. Upon the 'operation ot relay 211 a. circuit is 'closed from ground, inner lelt hand armature and lront contact of relay 211, winding ot relay 205 to battery and ground and relay 205 loolrs through its inner lett hand armature to the ground supplied by the upper contact ot dialing key 203. Relay 205 opens at its outer right hand armature, the circuit extending through the lower contacts oit dialing key 203, the lower outer armature and iront contact ot relay 202, conductor 115 to the winding of relay 116 so that the original en` ergizing circuit of this latter 'relay is opened. Vl-loweyer, relay 116 remains energized ir, a circuit controlled by the right hand ar1nature and front Contact of 'relay 211.

rlhe dialing circuit is new complete and may be traced troni 'ceilductor 404, the upper armature and baclc contact ot relay 40T, the norinal contacts of the upper armature of r lay 405, the Ytrent contact and upper arnia- 'i 1re et re ay 403, tip ot incl; 401.A tip oit plug` I* the normal lower contacts oit front 'ril lne* key 119, lront Contact d router lett hand armature ot relayA 103, alternate contact and outer leith-a'nd armature o'fi` relay 116, norinal contacts ot inner leit hand armature ot relay 121, left hand armature and `iront A"centact of relay 20S., normal contacts et the right hand ainiature oit relay 125, back contacts and lett hand armature ot relay 209, dial 129, winding et polarized relay 120, inner right hand armature and alternate Contact ot relay 116, alternate 'contact and inner right hand armature ot relay 103, ring ot plug 104, ring et jack 401, lower armature and :trent Contact 'ot relay 403, inner lower armature and back AContact of relay 405, rinsing et polari'ied relay 410, haelt Contact and lower armature ot. relay 40T Ato conductor 406. lC'onduc't'ors 404 and 400 lead to a toll switching trunk such for inst-ance as that shown in F 3 ot Patent 1ro. 1,543,685 to Stokely. As explained in such patent ground and battery are connected to these conductors through the lino :relay ot a selector switch so that current now flows over the circuit described to operate -such distant line relay but flows in such a 'direction that neither polarized relav 410 nor polarized relay 120 is energized. 'l The yoperator niay now dial the designation of. the called party whereupon the switches in the toll train will vbe actuated in the inanner fully explained in the patent to Stolcly No. 1,543,685.

lllhen the called line is seized' the current flow inthe dialing circuit is reversed and both relays 410 and 120 becoine energized. Upon the energization oli' relay 410 a circuit is established troni battery, 'armature and 1 avesse front Contact of relay 410, lower outer arina; turc, and of relay 405, winding o'l relay' 40d, to ground. Relay, 405 becomes energized and locks to the battery supplied by the right hand `armature of relay |402, whereupon relay 410 betoines in'ell'ect' e tlcatls any 'further change in this trunk circuit;

rlhe operation 'of relay 120 establishes a circuit troni battery, winding ot relay' 20G, front contact and armature of relay 120, normal contacts ot the right hand armature ot relay 20G, bacl Contact and Iout-er lett hand armature ol relay 121, conductor 113, armature and 'lront contact 'ofrclay' .111 to ground, causing the 4ener irlatitin t relay 20e. Reny ce new lacie nl a eil-ala. aan battery, winding of relay 206, outer left iand armature and front contact 0f relay 211, right hand armature and front contact of relay 20G, and thence over the circuit just described to the ground on conductor 113 supplied by the energization ot relay 111. Relay 206 in energizing establishes a circuit treni ground lett hand armature and 'trent co1' ct ot relay 201i, contacts of ltey 220, willen. of relay 20S to battery and ground. Relay 208 bcconies energized and opens the dialing circuit at its lett hand armature. rllhrough its right hand armature, relay 20S closes a circuit troni ground, arinature and trout Contact oit relay 210, front Contact and right hand arinature of relay 208, winding ot relay 219, to battery. Relay 219 becoming energized opens the original energizing circuit tor relay 211 but substitutes therefor a circuit iroin its own arinaturc to the winding of relay 211i l Relay 2053 is provided to automatically st artringing" on the toll switching trunk. Thi s isaccoinplishcd by the establishment ot a Circuit troni battery, resistance 21S`r trout Contact and lett hand arinati'irt of relay 208,

ii'ornial contacts ot the inner lett hand arma'- ture oit relay 121, outer lett hand armature and alternate contacts ot relay 11G, allernatc- Contact and outer lett hand armature ot relay 103r nornial lower contacts ot 'trent ringing key 119, tip ot plug 104.` tip ot jack 401, upper armature and iront Contact ot relay 408, upper armature and front Contact of relay 405, upper lett hand winding of repeating coil 421 winding ot relay 40T to ground. Relay 407- applies ringing;` current to the conductors 404 and 406 to call the called party in the manner Yfully described in the Stokcly patent above referred to.

Upon the operation of relay as above described the holding circuit of relay 207 which was traced through the back Contact of polarized relay 120 is opened and 4this relay becoming deenergized opens the circuit of relay 210. Relay 210, however, is slow to release and so holds over for an instant after rela-ys 206, 208 and 219 have become operated and relay 219 being also slow to release holds for an additional period of time after relay 210 releases its armature. Therefore after relay 20S has become energized time is counted. by relays 210 and 219 to hold relay 211 operated for a predetermined. period. At the end of this period relay 211 releases and in so releasing opens the circuit of relay 116 which thereupon returns to normal and. opens the ringing circuit established by relay 208. The release of relay 211 opens the holding circuit of relay 206 and this relay returns to normal. Relay 120 having returned to normal upon the energization of relay 208 there is no eircuit to maintain relay 206 energized, thus relay 407 is energized only for a predetermined length of time.

It has been stated that under normal conditions current through the windings oic the line relay of the distant selector switch flows through conductors 404 and 406. Upon the seizure of the called line this current flow is reversed causing the operation of relay 410 and 405. The operation oi relay 405 closes the circuit for the upper right hand winding oi repeating coil 421 so that relay 419 is now placed in series with the windings of the line relay of the distant selector switch and relay 419 thereby becomes operated. Relay 419 of the loop dialing trunk performs the same function as relay 319 oit the re- -peated dialing trunk, that is, closes a circuit through the right hand low resistance winding et' relay 402 and this in turn causes the operation of the supervisory lamp 124.

`lhen the called. party answers current is removed from the conductors 404 and 406 and relay 419 returns to normal. Tu doing so relay 419 opens the circuit through the right hand low resistance winding et relay 402 and causes the supervisory lamp 124 to become dark as an indication to the operator that a called party has answered.

At the end of the conversation the called party in replacing his receiver on its hook again causes the energization of relay 419 and thus closing the circuit through the right hand low resistance winding ot relay 402 causes the illumination of supervisory lamp 124 as an indication to the operator that the conversation has ceased. She thereupon removes plug 104 from jack 401 and by releasing relay 402 causes the loop dialing trunk relays to return to normal.

The circuit for energizing the automatic ringing start relay 208 was traced through the contacts of key 202. This key is provided 'lor night service operation where it is not desired to start ringing automatically. With key 220 actuated, then upon the operation oit' relay 206, relay 208 does not become operated. .Under these conditions, relay 419 becoming operated. closes a circuit through the left hand low resistance winding of relay 402 to cause the operation of supervisory lamp 124. This notities the operator that the called partys line has been seized and when the operator is ready she will actuate front ringing key 119. Thereupon a circuit will be extended from battery, resist-ance 218, conductor 132, alternate contacts et the lower contact set ot front ringing key 119, tip of plug 104, tip of jack 401, upper armature and front contact of relay 403, upper armature and front contact of relay 405, upper leil't hand winding et repeating coil. 421, winding ot relay 40T to battery and ground. Relay 407 becoming operated applies ringing current to the con ductors 404 and 406 to cause the ringing of the called partys telephone.

Under the conditions hereinbefore described, in relation to the operation et the automatic ringing start relay 208, it was noted that relaysl 210 and 219 counted time for the application of ringing current to the trunk line for a definite period ot time. It the called line when seized were busy, the application of ringing current would have no effect and since relay 407 only operated for a short and definite period ot' time, the trunk line will shortly revert to the condition in which it would be found -if the ringing relay 40h( had not been operated. Under this condition and described in the patent to Stokcly No. 1,548,685, relay 419 would be periodically energized and deenergized and this in turn would cause the periodic opera-- tion el supervisory lamp 124 to notify the operator that the called line is at this time busy.

lt may be mentioned here, in passing, that both relays 319 and 419 are provided with a left hand armature to which battery is connected upon its operation. This connection plays no part in the present invention being provided for causing the supervisory operation in connection with a different type cord circuit than that shown in F ig. 1.

During the time when the cord circuit shown in the upper part of Fig. 1 is in use, the operator may monitor on the cord by actuating key M. The operation of this key closes acircuit from ground, the lower set of contacts of key M, through the back contact and outer right hand armature of relay 204, winding ot relay 221 to battery and ground. The operation ot relay 221 connects the lett hand windingY of repeating coil 224 to the operators receiver. The upper and middle set of contact springs of the key M eonnectsthe tip and ring conductors et the cord circuit through the condenser 223 to the right hand windings et repeating coil 224 and in this manner the operator may listen to any conversation going on over the cord circuit, but cannot talk, since the trans initter circuit is cut oli" by the operation or relay 221.

It should he noted that when the key T fil is actuated and relay 111 becomes operated the ground for operating relay 111 also closes the circuit for the operation of the monitoring cut-ott1 relay E204 and connects the monitoring leads from the key M to the windings of repeating coil 215. rIhis feature is provided so that, while the operator has her common apparatus such as the supervisory control relays 109 and 110 for the front cord and the corresponding relays ifo-r the rear cord, together with the different keys such as the splitting key, thedial release key and the dialing key and the common dialing circuit connected to one cord, she may talk over another cord by merely throwing the monitoring key of such ,other cord. There are occasions when such operation is desir' ble as when, for instance, the operator is in the act of establishing a connection over one cord and is waiting :tor the called subscriber to answer. At such a time another connection on another cord may require attention and this can now be given by. operating the monitoring key of such other cord circuit.

The dial release key 201 is provided 'for releasing the dialing circuit under certain conditions. It will be noted that when the plug 104 has been inserted in a loop dialing trunk such as that shown in Fig. 4 that relay 211 becomes operated. Relay 211 in operating establishes a connection from ground, the alternate contacts of the inner lett hand armature of relay 211 to the holding circuit for relay 103, so that even though the operator releases her talking key T she may not restore the common apparatus including the dialing circuit to normal. It it is found necessary te do this, the operator will then depress the dial release key 201 which by opening its upper contacts will release relay 207 with the effect hereinbefore described.

Resistance 135 and condenser 136 comprise a balancing network which may be connected to the rear cord when the front ringing key 119 is operated. This balancing network performs the function ot balancing toll lines which may have repeaters connected thereto, in order to prevent singing. The balancing network is also .associated with the rear ringing key 134 so as to balance a toll line which may be connected to the front cord when the rear ringing key 134 is operated.

Vilhat is claimed is:

1. in a telephone system, a cord circuit for extending connections to trunk lines, trunk lines of diiferent character, automatic switches operable over said trunk lines, a switch controlling circuit associated with said cord circuit, and means in said controlling circuit for automatically adapting said controlling circuit to said diiterent character trunk lines.

2. In a telephone system, a cord circuit for extending connections to trunk lines, trunk lines of one character having a low resistance tip circuit, trunk lines oit another character having a high resistance tip circuit, automatic switches operable over said trunk lines, a switch controlling circuit associated with. said cord circuit, and a marginal relay arrangement in said controlling circuit for adapting said controlling circuit to said ditterent character trunk lines.

3. ln a telephone system, a cord circuit for extending connections to trunk lines. trunk lines 'ot different character,y said trunk lines and said cord circuit having a single character of supervisory means in their sleeve circuits, automatic switches operable over said trunk lines, a switch controlling circuit associated with said cord circuit, and means in said controlling circuit for automatically adapting said controlling circuit to said ditiicrent character trunk lines.

4. n a telephone system, a cord circuit for extending connections to trunk lines, trunk lines of one character having a low resistance tip circuit, trunk lines oit another character having a high resistance tip circuit, said trunk lines and said cord circuit ha ring a. single character oit supervisory means iu their sleeve circuits, automatic switches operable over said trunk lines, a switch controlling circuit associated with said cord circuit, and a marginal relay arrangen'ient in said controllin circuit 'for adapting said controlling circuit to said different character trunk lines.

5. ln a telephone system, a cord circuit for extending connections to trunk lines, trunk lines of different character, automatic .switchH es operable over said trunk lines, a switch controlling circuit normally (fliscrjmnccted from said cord circuit, means for ten'iporaril y connecting said controlling circuitI to said cord circuit, and means in said controllingcircuit for automatically adapting said controlling circuit to said diiicrent character trunk lines.

6. ln a telephone system, a cord circuit Vfor ext-ending connections to trunk lines, trunk lines ot one character having a low resistance tip circuit, trunk lines of another character having a high resistance tip circuit. automatic switches operable over said truuk lines, a switch controlling circuit normally disco nected from said cord circuit, means for temporarily connecting` said controlling circuit to said cord circuit, and a n'iarginal relay arangement in said controllin gl circuit for adapting said controlling circuit to said diterent character trunlr lines.

7. In a telephone system, a cord circuitlor extending connections to trunk lines, trunk lines of one character having a low resistance tip circuit, trunk lines oianother character having a high resistance tip circuit, said trunk lines and said cord circuit haring a single type et supervisory means in their sleeve circuits, automatic switches operable over said trunk lines, a switch controlling circuit normally disconnected from said cord circuit, means for temporarily connecting said controlling circuit to said cord circuit` and a marginal relay arrangement in said Controlling circuit dillcrentially respons to `said low resistance tip circuit and said l'iigh resistance tip circuit Afor adaptingr said controlling circuit to said different character trunk lines.

8. ln a telephone system, a cord circuit for extending connections to trunk lines, trunk lines of different character, automatic switches operable over said trunk lines, a switch controlling circuit connnon to said cord circuit, and means in said controlling circuit for automatically adapting said controlling circuit to said different character trunk lines.

9. ln a telephone system, a cord circuit for extending connections to trunk lines, trunk lines of one character having a low resistance tip circuit, trunk lines ot another character having a high resistance tip circuit,r auto-- matic switches operable over said trunk lines, a switch controlling circuit common to said cord circuit, and a marginal relay arrangement in said controlling circuit differently responsive to said low resistance tip circuit and said high resistance tip circuit tor adapting said controlling circuit to said different character trunk lines.

l0. In a telephone system, a cord circuit comprising in normal condition a clear pair et conductors only 'for a talking circuit and a third conductor including supervisory means, trunk lines ot different character accessible to said cord circuit, automatic switches operable over said trunk lines, a switch controlling circuit 'tor association with said cord circuit, and means in said controlling circuit for automatically adapting said controlling circuit to said different character trunk lines.

ll. In a telephone system, a cord circuit comprising in normal condition a clear pair ot conductors only for a talking circuit and a third conductor including supervisory means, trunk lines of one character having a loiv resistance tip circuit, trunk lines of another character having a high resistance tip circuit, automatic switches operable over said trunk lines, a switch controlling circuit t'or associati-cn with said cord circuit, and a marginal relay arrangement in said con trolli g circuit selectively responsive to said lovv resistance tip circuit and said high resistance tip circuit for adapting said controlling circuit te said different character trunk lines.

l2. In a telephone system, a cord circuit, a trunk line accessible to said cord circuit, automatic switches operable over said trunk line, a switch controlling circuit common to said cord circuit, a polarized relay in said controlling circuit responsive to the setting ot a switch, a relay responsive to said polarized relay for applying ringing current to said trunk line, and a plurality of relays tor counting time tor limiting the energization ot said last relay to a predetermined period ot' time.

i3. In a telephone system, a cord circuit, a trunk line accessible to said cord circuit, a ringing relay in said trunk line ior applying ringing current to said trunk, automatic switches operable over said trunk line, a switch controlling circuit common to said cord circuit, a polarized relay in said controlling circuit responsive to the setting ot a switch, a relay responsive to said polarized relay tor operating said ringing relay, and a plurality of relays for counting time for limiting the energization of said last relay to a predetermined period ot time.

14, In a telephone system, cord circuits each including an individual listening key and individual talking key, control circuits and apparatus includingl an operators t ansmitter and receiver common to said cord circuits, means responsive to the actuation ot a listening' key, for associating said operators receiver only with the corresponding' cord circuit, means responsive to the actuation olf a talking key for exclusively associating said common circuits and apparatus with the corresponding cord crcuit, and means responsive to the actuation ot a listening key Ot one cord circuit during the operation of a talking key Ot' another cord circuit for associating both the said transmitter and thesaid receiver With the said one cord circuit.

l5. ln a telephone system, cord circuits each including` an individual listening key and an individual talking key, controlling circuits and apparatus including an operators transmitter and receiver common to said cord circuits, means responsive to the actuation ott a listening key for associating said operators receiver with the corresponding cord circuit, a relay responsive to the said actuation of said listening key for cutting ott the said operators transmitter, means responsive to the actuation of a talking key tor exclusively associating said common circuits and apparatus with the correspending` cord circuit and means responsive to the actuation of a. listening key ot one cord circuit during the operation of a talking key ot another cord circuit for associating both the said transmitter and the said receiver With the said one cord circuit.

16. ln a telephone system, cord circuits each including an individual listening key and an individual talking key, controlling circuits and apparatus including an operators transmitter and receiver common to said cord circuits, means responsive to the actuation of a listening key for connecting said operators receiver to the Corresponding corel circuit, a relay responsive to the said actuation `oit the said listening key for cuttingy off the said operators transmitter' and Ineans responsive to the actuation of a talking key forexclusively associating' said coin- -zO gez/.5,956

mon circuits and apparatus with the corresponding cord circuit, said last means including a relayfor rendering ineffective said irst relay.

ln witness whereof, I hereunto subscribe iny naine this 24 day of May, A. D. 1927.

LESLIE F. PORTER. 

